1. Field of the Invention
The present invention relates to a tonometer for measuring intraocular pressure, and more particularly to a load-sensing type tonometer which measures intraocular pressure by applying pressure onto an eye being examined via its eyelid, and detecting the load being applied.
2. Description of the Prior Art
There are contact type and non-contact type conventional intraocular pressure measurement systems. In a contact type system a measuring member is pressed directly against the eyeball, and the pressure required to produce a given degree of deformation is used to establish the intraocular pressure. In the non-contact type system a stream of air is blown onto the surface of the cornea and the corneal deformation thus produced is measured, usually by an optical technique.
Contact type systems today offer a high degree of reliability. However, requiring as they do that part of the system apparatus be brought into direct contact with the cornea, a problem with contact type systems is that unless the operator is skilled in its operation, there is a risk that the cornea may be damaged.
While with the non-contact type system there is less risk of damaging the cornea, blowing a stream of air onto the cornea causes the patient to feel fear and discomfort. Thus, while it is called a non-contract method, this only means that there is no direct mechanical contact with the cornea. However, inasmuch as the measurement procedure involves subjecting the cornea to the direct application of force, it is no different from the contact type described above.